294 OBGANOGEAPHY. 



monly termed the nut, is the endocarp ; and the green covering 

 of this, called the husk, consists of mesocarp and epicarp combined. 

 In the Orange, the outer separable rind is composed of mesocarp 

 and epicarp ; and the thin membranous partitions which divide 

 the pulp into separate portions form the endocarp ; the edible 

 pulp itself, as already noticed, is a development of succulent 

 parenchyma from the inner lining of the ovary, or probably 

 from the placentas only. In the above fruits, and numerous 

 others might be quoted, the different layers of the pericarp are 

 more or less evident, but in some cases, as in the Nut, these 

 layers become so blended, that it is difficult, if not impossible, 

 to distinguish them. The examples of fruits now mentioned, 

 together with those previously alluded to, will show in a strik- 

 ing manner the very varying nature and origin of the parts 

 which are commonly eaten. 



Sutures. — In describing the structure of the carpel, we found 

 that the ovary presented two sutures ; one of which, called the 

 ventral suture, corresponded to the union of the margins of the 

 lamina of the carpellary leaf, and was consequently turned 

 towards the axis or centre of the flower; and another, termed 

 the dorsal suture, corresponding to the mid-rib of the lamina, 

 and which was directed towards the circumference. The simple 

 fruit being formed, in most cases, essentially of the mature 

 ovary, also presents two sutures, which are distinguished by 

 similar names. These, like those of the ovary, may be frequently 

 distinguished externally, either by a more or less projecting line, 

 or by a slight furrow; thus in the Peach (fig. 679), Cherry, 

 Plum, and Apricot, the ventral suture is very evident, although 

 the dorsal suture has become nearly effaced ; while in the Bladder 

 Senna {fig. 648), Pea, and other fruits of the Leguminosse, both 

 dorsal and ventral sutures are clearly visible externally. 



In a compound ovary with two or more cells, in which the 

 placentation is axile, it must be evident, of course, that the dorsal 

 sutures can alone be observed externally, as the ventral sutures 

 of the component ovaries are turned towards, and meet in the 

 axis of the flower, and are hence removed from view; the 

 number of dorsal sutures will also necessarily correspond to the 

 number of component ovaries of which such an ovary is formed. 

 In a fruit presenting similar characters, we find of course a 

 similar disposition of the sutures. When an ovary, on the con- 

 trary, is formed of the blades of two or more carpellary leaves, 

 the mai^ins of which are not inflected, or only partially so, and 

 therefore one-celled, and the placentation parietal or free central, 

 both ventral and dorsal sutures may be observed externally 

 alternating with each other. The fruit, which is formed in 

 a similar manner, necessarily presents a similar alternation of 

 the sutures on its external surface. 

 Dehiscence. — The pericarp at varying periods, but commonly 



